Who's got the power? The spread of VoIP over Wi-Fi could depend on battery life

Effective handsets will provide the key to market acceptance


Effective handsets will provide the key to market acceptance

Internet telephony using wireless technologies such as Wi-Fi and Wimax is still at the start of the growth curve. Nevertheless, it offers many opportunities for corporate customers - and some headaches for mobile operators.

When technology trends experience huge success, it can only be a matter of time before they come together. Take voice over IP and wireless networks. VoIP, which was a technology-in-waiting for years, has finally gone mainstream. Products like Skype have captured the public's imagination, while US-based VoIP company Vonage formally opened its UK operation in May. With wireless networking exploding in the past couple of years, using wireless links for voice over IP calls seems like a no-brainer.

VoIP over Wi-Fi (VoWi-Fi) has potential in the enterprise WLan as a means of reducing telephony costs while freeing employees from their desks. But it carries even greater potential for mobile workers wanting to make cheap calls from the growing number of public hotspots. Analysts are starting to acknowledge the mid-to long-term opportunities for VoWi-Fi, but there is still much work to be done.

IT managers thinking of VoWi-Fi for their corporate communications could benefit from dramatic cost reductions for mobile employees, if analysts and consultants are to be believed. Apart from savings for calls made in the UK, it offers a drastically cheaper alternative for employees roaming outside of their home mobile network.

"We do think there are some advantages for enterprises to move to voice over Wi-Fi," says Jawad Shaikh, head of the Capgemini Telecom Media & Entertainment Strategy Lab. "Our calculations show that users could save up to 24% on their mobile bills by switching to voice over IP via Wi-Fi."

The problem with Wi-Fi has always been convenience. Today, VoIP calls are often made with a PC and a headset, although the popular VoIP software client Skype is now available for the Pocket PC, enabling Wi-Fi-enabled PDA users to take advantage of the technology. The sweet spot for VoWi-Fi, however, will be the introduction of cellular phones that offer both cellular and Wi-Fi capabilities.

Dual mode handsets have been science fiction until recently, and even now they are rare and relatively expensive, argues Shaikh. Battery life has been the biggest barrier to the introduction of the dual purpose handsets, argues Ian Shepherd, solutions manager for Telindus. "Wi-Fi compared to cellular is power hungry," he warns. "A cellphone will run for three days or a week on standby, whereas when you're talking on a Wi-Fi phone, until recent developments in low-power chipsets, you'd be lucky to get 20 minutes out of it."

Nevertheless, they are beginning to appear as companies iron out the problems. British Telecom signed a deal last year with Vodafone under which it would become a mobile virtual network operator (MVNO). The company planned a Bluetooth-based mobile handset called the Bluephone which would switch between Vodafone's network and broadband VoIP using a home-based access point. The company is also making the Bluephone Wi-Fi-friendly. Meanwhile, Motorola's Wi-Fi phone, the CN620, is already shipping. The only snag is that it requires proprietary hardware to work with a Wi-Fi network and won't operate with a standard Wi-Fi hotspot. NTT DoCoMo is shipping a more standard version in the form of its N900il device, which is aimed at corporate users.

Wireless will make waves

Analyst company ABI Research believes the annual global sales of dual mode mobile phones will exceed 100 million by 2010. Shaikh is even more optimistic, predicting the same figure in 2008, which he says will account for nearly 5% of the expected 2 billion mobile subscriber base worldwide. By then, he argues that Wi-Fi penetration will have reached 35% to 40% of broadband-enabled homes, creating an even more attractive proposition for users of the handset who can make inexpensive calls at home.

One of the biggest problems for such handsets in the short-term is the handing off of calls from Wi-Fi networks to cellular networks and vice versa without dropping the conversation. If a mobile worker is making a VoIP call and walks out of the building, it would be nice to switch automatically to the cellular service. Gary Mead, vice president international of SpectraLink, which supplies Wi-Fi- and Ethernet-based IP handsets for a variety of suppliers, says that companies have a long way to go before they address this issue. "We can see some of the trial systems that have come out, and they recognise that it's a bit of a problem and it hasn't been solved," he says.

For that to happen, cellular network operators must be prepared to play ball, and yet people like Mike Short, head of R&D at O2, seem lukewarm at best about the idea. "I'd raise questions about what workers want to do, because it may not be the best solution for the business," he says, adding that the company won't talk about this with customers until 2006 at least, because the lack of dual mode handsets makes it too early. "Jumping to dual mode may cause complications," he adds.

But why are mobile operators acting like plumbers, looking at seamless VoWi-Fi/cellular handoffs, shaking their heads and sucking air through their teeth? It is because they make profits by capitalising on revenue from circuit-switched mobile calls. Although Short calls VoWi-Fi a complementary technology (after all, O2 runs its own wireless hotspots), it's really a threat to mobile operators.

Capgemini's Shaikh argues that between 5% and 7% of mobile operators' traditional voice-based revenues will be threatened by VoWi-Fi in 2008. "Those revenues will be cannibalised, so they will disappear, basically. If you get voice over wireless Lan, typically for enterprise customers, this will be basically free." The problem is that while mobile operators could pick up those revenues by offering subscription services to their wireless hotspots, they could just as easily lose them to another hotspot supplier- or to one of the burgeoning community of broadband wireless access suppliers [see box]. Voice services still constitute the lion's share of revenue from the 3G networks that cost the operators so much to build, and Shaikh argues that VoIP calls via 3G data connections are not currently viable for performance and pricing reasons. This positions VoWi-Fi as a disruptive technology that operators have to manage as best they can.

While the conflict between mobile operators and other VoWi-Fi providers brews in the streets, VoWi-Fi offers some advantages within the corporate Lan, suggests Pierre Trudeau, chief technical officer and founder of the Colubris Networks, which sells back-end communication products including VoWi-Fi systems.

One of the biggest advantages of VoWi-Fi in the Lan environment is the ability to have a single mobile phone to take a call when you are away from your desk rather than having to redirect calls to a mobile phone even though you are in the building, he says.

Advantages over Dect

Traditional Dect phones do that, but VoWi-Fi handsets can provide benefits that Dect cannot. "It gives you not only a voice wireless network but also a data network," Trudeau explains. This means that workers in a warehouse or campus environment, for example, could tap into supply chain management systems on the same device that they use for phone calls, thereby increasing convenience.

Being able to tell which access point a VoWi-Fi handset is near also carries the potential to take calls while moving around a building. SpectraLink's Mead says that developer partners can build location-based services into WLan phone handsets. For example, BlueSky Wireless has developed a worker monitoring system that can be used to plot the location of employees to the nearest access point - useful in industries such as construction, chemicals and oil and gas. The company will also produce bespoke software for raising alarms and controlling stock using wireless VoIP handsets.

Nevertheless, there are still challenges for IT departments to overcome when implementing VoWi-Fi within the corporate WLan. For example, device contention and quality of service are critical - compromises on call reliability and quality will lead to rapid disillusionment among staff. There are ways around this, says Trudeau. His system can dynamically load balance among access points, increasing the radio coverage of a particular access point to take the load when one near it is running at full capacity.

There are two main standards used to maintain the quality of service on VoWi-Fi calls. The first, the SpectraLink Voice Priority protocol (SVP), gives priority to voice packets, but even SpectraLink's Mead expects this to disappear in the long term as the standards become more mature. The leading contender is the Wi-Fi multimedia (WMM) protocol, defined by the Wi-Fi Alliance as a quality of service protocol for voice, video, and audio applications. Designed as a profile of the forthcoming IEEE quality of service extensions for 802.11 networks, it is starting to gain ground among manufacturers.

Quality of service won't do you any good at all if you move from one wireless access point to another while making a VoIP call only to find that your network signal drops out.

Traditionally, moving between access points requires you to reacquire a network connection, but this will not be acceptable in enterprise VoWi-Fi environments. Instead, companies like Colubris have developed systems that retain the network connection at a central point and cache wireless network access keys in nearby access points so that the connection doesn't drop.

VoWi-Fi may still be in its early stages, and the growth will be slow thanks to the poor availability of dual mode handsets. However, as these handsets become more prevalent in the next 18 months, we are likely to see growing interest in the technology and the slow but steady adoption of VoWi-Fi among mobile users.

Read more on Wireless networking